Plugin creates thumbnails to “x_old” only

Hi there,
We’ve been using your plugin which is really the only tool that exist for shops with different picture’s ratios.
We are running latest WordPress & Woocommerce.
It is now no longer creating the desired thumbnails. Looking at “Regenerate thumbnails” list, we can see:

woocommerce_single: 600×600 pixels (proportionally resized to fit inside dimensions) SAZ-BLCMF-DPA-Professional-Turkish-Long-saz-ebony-pegs-walnut-wood-fishman-pickup-9-405x600.jpg
woocommerce_single (old): 600×600 pixels SAZ-BLCMF-DPA-Professional-Turkish-Long-saz-ebony-pegs-walnut-wood-fishman-pickup-9-600x600.jpg

So the old Woocommerce shop_single is being created currectly (600px X 600px), but the new “woocommerce_single” gives 405px X 600px. This is causing our theme, which displays the new term, to show the wrong thumbnails.

We are also using your advice from on the posts here to force 600px X 600px with this snippet:

add_filter('woocommerce_get_image_size_single', function($size){
    $size['height'] = 600;
    $size['width'] = 600;
    return $size;
});

Would love to hear your opinion as we are now stuck without proper thumbnails.
Thanks a ton,
D.